Hi y'all.
I just noticed these today, these round things on the sides of the hydraulic fluid reservoirs for my front brake and for my clutch. It appears as if these may actually be windows designed for easy checking of fluid levels inside the reservoirs. I can't confirm this though because there seems to be 24 years of hardedned road grime on these windows. I haven't attempted to clean them yet for fear of using too much pressure on them and causing breakage. I was wondering what the best way to clean these would be and if it's actually safe to do so.